Congestive heart disease is a progressive and debilitating illness. The disease is characterized by a progressive enlargement of the heart. As the heart enlarges, the heart is performing an increasing amount of work in order to pump blood during each heart beat. In time, the heart becomes so enlarged that it cannot adequately supply blood. An afflicted patient is fatigued, unable to perform even simple exerting tasks and experiences pain and discomfort. Furthermore, as the heart enlarges, the internal heart valves cannot adequately close. This impairs the function of the valves and further reduces the heart's ability to supply blood.
Causes of congestive heart disease are not fully known. In certain instances, congestive heart disease may result from viral infections. In such cases, the heart may enlarge to such an extent that the adverse consequences of heart enlargement continue after the viral infection has passed and the disease continues its progressively debilitating course.
Patients suffering from congestive heart disease are commonly grouped into four classes (i.e., Classes I, II, III and IV). In the early stages (e.g., Classes I and II), drug therapy is a commonly proscribed treatment. Drug therapy treats the symptoms of the disease and may slow the progression of the disease. However, even with drug therapy, the disease will typically progress. Furthermore, the drugs sometimes have adverse side effects.
One relatively permanent treatment for congestive heart disease is heart transplant. To qualify, a patient must be in the later stages of the disease (e.g., Classes III and IV with Class IV patients given priority for transplant). Such patients are extremely sick individuals. Class III patients have marked physical activity limitations and Class IV patients are symptomatic even at rest.
Due to the absence of effective intermediate treatment between drug therapy and heart transplant, Class III and IV patients often suffer before qualifying for heart transplant. Furthermore, after this suffering, the available treatment is often unsatisfactory. Heart transplant procedures are risky, invasive and relatively expensive, and often extend a patient's life by only relatively short times. For example, prior to transplant, a Class IV patient may have a life expectancy of six months to one-year. Heart transplant can improve the expectancy to about five years. Unfortunately, not enough hearts are available for transplant to meet the needs of congestive heart disease patients. In the United States, in excess of 35,000 transplant candidates compete for only about 2,000 transplants per year. A transplant waiting list can be about eight to twelve months long on average and frequently a patient may have to wait about one to two years for a donor heart. Even if the risks and expense of heart transplant could be tolerated, this treatment option is becoming increasingly unavailable. Furthermore, many patients do not qualify for heart transplant for failure to meet any one of a number of qualifying criteria.
Congestive heart failure has an enormous societal impact. In the United States alone, about five million people suffer from the disease (Classes I through IV combined). Alarmingly, congestive heart failure is one of the most rapidly accelerating diseases (about 550,000 new patients in the United States each year). Economic costs of the disease have been estimated at $38 billion annually.
Substantial efforts have been made to find alternative treatments for congestive heart disease. A surgical procedure referred to as the Batista procedure includes dissecting and removing portions of the heart in order to reduce heart volume. This procedure is the subject of some controversy. It is highly invasive, risky and relatively expensive and commonly includes other relatively expensive procedures (such as a concurrent heart valve replacement). Also, the treatment is limited to Class IV patients and, accordingly, provides limited hope to patients facing ineffective drug treatment prior to Class IV. Furthermore, the consequences of a failure of this procedure can be severe.
There is, therefore, a need for alternative treatments applicable to either or both the early and later stages of congestive heart disease to either stop or slow the progressive nature of the disease. Cardiomyoplasty is a treatment for relatively early stage congestive heart disease (e.g., as early as Class III dilated cardiomyopathy). In this procedure, the latissimus dorsi muscle (taken from the patient's shoulder) is wrapped around the heart and chronically paced synchronously with ventricular systole. Pacing of the muscle results in muscle contraction to assist the contraction of the heart during systole.
While cardiomyoplasty has produced symptomatic improvement, the nature of the improvement is not fully understood. For example, one study has suggested the benefits of cardiomyoplasty are derived less from active systolic assist than from remodeling, perhaps because of an external elastic constraint. The study suggests an elastic constraint (i.e., a non-stimulated muscle wrap or an artificial elastic sock placed around the heart) could provide similar benefits. Kass et al., Reverse Remodeling From Cardiomyoplasty In Human Heart Failure: External Constraint Versus Active Assist, 91 Circulation 2314-2318 (1995).
Even though cardiomyoplasty has demonstrated symptomatic improvement, at least some studies suggest the procedure only minimally improves cardiac performance. The procedure is invasive, requiring harvesting a patient's muscle and an open chest approach (i.e., sternotomy) to access the heart. The procedure is also complicated. For example, it is sometimes difficult to adequately wrap the muscle around the heart with a satisfactory fit. Also, if adequate blood flow is not maintained to the wrapped muscle, the muscle may necrose. The muscle may stretch after wrapping, thereby reducing its constraining benefits, and is generally not susceptible to post-operative adjustment. In addition, the muscle may fibrose and adhere to the heart causing undesirable constraint on the contraction of the heart during systole.
Mechanical assist devices have been developed as intermediate procedures for treating congestive heart disease. Such devices include left ventricular assist devices (“LVAD”) and total artificial hearts (“TAH”). An LVAD includes a mechanical pump for urging blood flow from the left ventricle and into the aorta. An example of a device of this type is shown in the Arnold U.S. Pat. No. 4,995,857. TAH devices, such as the known Jarvik heart, are used as temporary measures while a patient awaits a donor heart for transplant.
Other cardiac assist devices are disclosed in the Lundback U.S. Pat. No. 4,957,477, Grooters U.S. Pat. No. 5,131,905 and Snyders U.S. Pat. No. 5,256,132. Both the Grooters and Snyders patents disclose cardiac assist devices which pump fluid into chambers opposing the heart to assist systolic contractions of the heart. The Lundback patent teaches a double-walled jacket surrounding the heart. A fluid fills a chamber between the walls of the jacket. The inner wall is positioned against the heart and is pliable to move with the heart. Movement of the heart during beating displaces fluid within the jacket chamber.
The commonly assigned Alferness U.S. Pat. No. 5,702,343 discloses a cardiac support device, sometimes referred to as a jacket, that constrains cardiac expansion to treat congestive heart disease and associated valvular dysfunction. One embodiment of the jacket is formed of a knit material of polyester having specific compliance and other material characteristics (including elasticity) more fully described in the Alferness et al. U.S. Pat. No. 6,482,146. Another embodiment of the jacket has a base end with a hem material of double layers as described in the Nauertz et al. U.S. Pat. No. 6,155,972.
Jackets of the types described in the Alferness et al. U.S. Pat. No. 6,482,146 and Nauertz et al. U.S. Pat. No. 6,155,972 have been demonstrated to be capable of providing effective treatment for congestive heart failure in certain patients. Surgical procedures for placing the jacket on a diseased heart include a full sternotomy in which the sternum or breast bone of the patient is cut and separated to provide an open-field access to the heart. During such an open procedure, a surgeon has direct visualization and a wide field of access to the heart. The base end of the jacket is opened and placed over the apex of the heart with the base end advanced to the atrial-ventricular groove (A-V groove). The surgeon can then secure the base end in the desired position through sutures or the like. It is noted in the Alferness U.S. Pat. No. 5,702,343 that other suitable securing arrangements include a circumferential attachment device such as a cord, suture, band, adhesive or shape memory element which passes around the circumference of the base of the jacket. The ends of the attachment device can be fastened together to secure the jacket in place.
Also, the surgeon can adjust the jacket on the heart by gathering any excess material and suturing the excess material together to get a desired amount of tension of the jacket on the heart. The Alferness U.S. Pat. No. 5,702,343 also describes an alternative approach in which the jacket includes a mechanism for selectively adjusting the volumetric size of the jacket. A slot that opens on the base of the jacket and extends toward the apex end is described as one mechanism for providing the size adjusting function. Adjustment mechanisms are also disclosed in the Shapland et al. U.S. Pat. No. 6,425,856 and the Kung et al. U.S. Pat. No. 6,508,756. Other cardiac support devices are disclosed in Lau et al. U.S. Pat. Nos. 6,595,912 and 6,612,978.
While the open-chest implantation procedure is acceptable, it is desirable to be able to place a jacket on the heart through laparoscopic or other less-invasive procedures. During less-invasive procedures, the surgeon may have more limited access to the heart and more limited ability to ensure placement and alignment of a jacket on the heart. Properly placing and securing the jacket on the heart during minimally-invasive delivery procedures of these types can be more difficult than in open-chest procedures.
There is, therefore, a continuing need for improved structures for securing jackets or other cardiac support devices to the heart. In particular, there is a need for improved structures for attaching and fitting the devices to the heart. Structures of these types that are self-adjusting would be especially desirable. The structures should be capable of providing the attaching and/or fitting functions without interfering with the therapeutic functions of cardiac support devices. Structures that meet these objectives and can be used in connection with minimally-invasive delivery procedures would also be desirable.